Field of the Invention
The present invention lies in the field of vehicle seats, and in particular aircraft seats. The present invention provides an aircraft seat having a stand that is capable of absorbing deformation of the floor of the aircraft, in particular in the event of a violent landing or indeed of a crash.
Description of Related Art
Any seat in an aircraft must provide protection to the passenger occupying the seat, in particular in the event of a violent landing or indeed of a crash. In particular, the seat must absorb violent impacts and/or strong vertical deceleration to which the aircraft might be subjected.
For this purpose, aircraft seats incorporate passenger protection means commonly constituted firstly by the structure of the seat and secondly by one or more energy absorber devices. An energy absorber device serves to dissipate some or all of the kinetic energy that is stored in the passenger of the seat when the seat is subjected to violent impacts and/or strong deceleration, in particular in the event of a crash. Such an energy absorber device serves to limit bodily injury to the passenger of the seat, in particular compression of the spinal column.
In a common embodiment, a seat comprises a stand, a bucket including both a seat pan and a seat back, and one or more energy absorber devices. The stand is anchored to the floor of the aircraft via a plurality of fastening points and it supports the bucket, which may possibly slide relative to the stand. One or more energy absorber devices connect the bucket to the stand. Starting from a force corresponding to a certain level of deceleration, the bucket is thus capable of sliding relative to the stand in order to dissipate part of the energy. By way of example, the stand may be made up of two L-shaped legs to which the bucket is fastened.
An energy absorber device generally comprises deformable support means, such that the bucket is held firmly in a situation of normal use. In the event of a crash, the strong deceleration to which the aircraft is subjected deforms the support means, thereby leading to downwardly directed sliding of the bucket relative to the stand. As a result, at least a portion of the energy to which the passenger is subjected during a crash is dissipated by deforming the support means. Deformation of the support means is referred to as “deployment” of the energy absorber device. By way of example, an energy absorber device is described in Document FR 2 930 613, and Document FR 2 930 520, describing an aircraft seat fitted with such a device.
Furthermore, in order to qualify as a seat for aviation, the applicable regulations and standards require static pre-stress to be introduced into the structure of the seat during validation testing in order to simulate the effect on the seat of deformation of the floor as occurs during a crash. The seat must be structured to absorb the kinetic energy of the passenger in compliance with the requirements of aviation regulations, while accommodating said deformation of the floor and without separating from the floor.
The application of floor deformation to the stand of the seat leads to the stand being deformed, with this being transmitted to the mechanical connections between the stand and the bucket, and consequently to the bucket. The bucket, and consequently both the pan and the back are subjected in particular to twisting, and that twisting may be considerable. Such stressing of the stand and twisting imparted to the bucket and its mechanical connections with the stand lead to large effects on the seat and its components.
Firstly, the application of such deformation from the floor to the stand causes static mechanical stresses to appear in the components of the seat, and in particular in the fastenings between the stand and the floor, in the means for connecting and guiding the bucket relative to the stand, and finally in the bucket itself.
In particular, these static mechanical stresses that appear as a result of the floor deforming can lead to a malfunction of the energy absorber device, such as partial deployment with limited energy dissipation, or indeed complete blocking of the energy absorber device. Consequently, in the event of an impact, the energy absorber device no longer performs its function in full and does not absorb the expected amount of energy.
Furthermore, such deformation of the floor can also lead to friction appearing in the means for guiding the bucket relative to the stand. This friction is an internal friction phenomenon within the guide means, which friction is difficult to control and leads to jerky catching and/or sliding phenomena between the sliding elements constituting such guide means, or indeed to them becoming totally jammed. Such friction can then lead to random operation of the energy absorber devices, thereby degrading the quality with which energy is absorbed during a crash.
Likewise, hammering or swarf-generating phenomena can also appear in the guide means and can cause them to malfunction, and consequently can lead to random operation of the energy absorber devices.
In particular, sudden variations in energy absorption can occur, giving rise to peaks of force in a passenger's spinal column, which may be fatal.
Accommodating such deformation of the floor thus requires the components of the seat to be overdimensioned and requires the connection and guide means to be complex in order to ensure that the seat operates correctly during a crash. This thus involves the guide means and the sliding elements being reinforced, and being designed in particular so as to limit the appearance of friction.
Furthermore, as a result of the bucket twisting, the pan and the back present contact surfaces with the passenger that become deformed, having the consequence of the passenger sliding and/or being positioned asymmetrically during a crash. Such positioning of the passenger leads to random movements of the passenger's body that can generate additional forces on the limbs, in particular on joints, leading to additional bodily injuries.
Furthermore, Document FR 2 495 101 describes an aircraft seat comprising a bucket having a pan and a back, a support connecting the bucket to the floor, a practically undeformable box secured to the bucket, and a plurality of energy absorber devices. That seat makes it possible to dissociate the energy absorber devices vertically and horizontally so that they are independent of the state of twisting of the floor. Nevertheless, the support does not prevent the stresses that result from the floor twisting being transmitted to the bucket and to its components.
Document WO 2008/073035 describes a vehicle seat having a triangular pan and a back to which the pan is connected by revolute joints. The front of the seat is connected via a revolute joint to a front support fastened to the floor of the vehicle, while the back is connected directly to the floor by revolute joints. The pan and the back are tubular structures. The seat is thus fastened to the floor at three points via three revolute joints.
Document FR 2 735 096 describes a swivel seat for a vehicle, in particular an aircraft. The swivel seat comprises a base that is fastened to the floor of the vehicle and provided with a top turntable, and also a pan that is fastened to the top turntable via declutchable connections allowing the pan to move parallel to the top turntable. The base also includes at least two components connected to the top turntable and hinged about orthogonal hinge axes that are parallel to the top turntable. The base thus makes it possible to avoid twisting of the floor that exceeds a certain limit leading to deformation of the pan, or indeed to the pan escaping from the base.
Document U.S. Pat. No. 3,582,133 describes a vehicle seat, in particular for a car. That seat is fastened to the floor at three points via three revolute joints and it includes at least one energy absorber device. Each energy absorber device is arranged between the seat and one of the fastening points with the floor. Furthermore, the floor may include a deformable zone at at least one of the fastening points in order to dissipate a portion of the energy in the event of an impact.
Furthermore, Document GB 2 313 214 describes a vehicle seat provided with an active suspension device for limiting movements of the seat during movements of the vehicle. The seat includes an understructure formed by actuators and connected via ball joint connections firstly to a support that is secured to the seat, and secondly to the floor of the vehicle.
Furthermore, Document U.S. Pat. No. 4,128,217 describes a support for fastening a seat on the floor of an aircraft while serving to isolate the seat from deformation of the floor in the event of the aircraft crashing.
Finally, the technological background of the invention includes Documents US 2013/228652 and EP 0 679 573, which describe energy absorber seats for aircraft, and also Document WO 2013/076255, which describes an extensible connection element for fastening a seat to the floor of a vehicle.
Furthermore, certain additional requirements need to be taken into account when designing and selecting a seat for a vehicle, and in particular for an aircraft.
Firstly, the space occupied by the seat needs to be minimized, e.g. in order to make it easier to install in the cabin of the vehicle, in particular in order to optimize the number of seats that can be installed in the cabin. Furthermore, the weight of the seat must also be minimized in order to limit its effect on the weight of the vehicle. Finally, the structure of the seat must be as simple as possible in order to limit its weight and the cost of fabricating the seat.